Posttraumatic stress disorder (PTSD), depression, alcohol use disorders (AUD), traumatic brain injury, and chronic pain frequently co-occur among post-9/11 war Veterans and are associated with functional impairment and suicide risk. Yet, no treatment exists [that was specifically designed] to promote functional recovery in Veterans experiencing any combination of these most common mental and physical wounds of war. This is the re-submitted proposal for a second competitive renewal to fund Phase 3 of Project SERVE (Study Evaluating Returning Veterans? Experiences). In Phase 1 (RX000304-01A1), we identified risk and resilience factors for deployment-related mental health conditions regardless of whether those factors were modifiable. In Phase 2 (RX000304-04A1), we refined our approach by focusing on modifiable predictors drawn from the treatment outcomes literature. The over-arching aim of this programmatic line of research is to inform the development of evidence-based prevention and treatment programs designed to assist returning Veterans with achieving optimal functioning upon reintegrating into civilian life. This vision comes to fruition in the proposed Phase 3, which proposes both to extend the longitudinal study (Aim 1) and to adapt, refine, and pilot test an intervention to promote functional recovery (Aim 2). The 2-year longitudinal study (N = 500) will examine novel factors (e.g., mindfulness, perceived burdensomeness, thwarted belongingness, moral injury) and established treatment targets (psychological flexibility, self-compassion, emotion regulation) in relation to latent class trajectories of functional impairment, and as predictors of risk for self-directed violence (SDV; i.e., suicide risk), which is a top priority for VA and RR&D. In the prior Phases, we established psychological inflexibility as a robust risk factor for mental health problems, functional impairment, and SDV. Thus, in Aim 2, using a Successive Cohort Design, we will adapt, refine [based on Veterans? feedback], and pilot-test an adapted evidence-based intervention, Acceptance and Commitment Therapy (ACT) that targets psychological flexibility to promote functional recovery (ACT-FX). We previously demonstrated the promise of ACT, a transdiagnostic, mindfulness and acceptance-based behavior therapy aimed at improving functioning by increasing psychological flexibility with Veterans with co-occurring PTSD-AUD. We will test the feasibility and acceptability of ACT-FX, [an individually-tailored intervention to promote functional recovery related to these commonly co-occurring conditions as compared to mental health treatment as usual (TAU) in 60] Veterans with moderate-to-severe functional impairment. Our ultimate goal is to help shift chronically impaired Veterans to a recovery trajectory. Integrating data from the longitudinal study (Aim 1) with data from the treatment study (Aim 2), we will conduct a preliminary test of whether ACT-FX is associated with functionally impaired Veterans moving to a latent class trajectory characterized by long-term recovery (Aim 3; Exploratory).